FIG. 1 is a top view of a conventional multilayer ceramic capacitor with interposer, FIG. 2 is a partial cross sectional side view of the multilayer ceramic capacitor with interposer shown in FIG. 1, and FIG. 3 is a partial cross sectional side view of the multilayer ceramic capacitor with interposer shown in FIG. 1 and FIG. 2, being mounted on a substrate.
It should be noted that, in the explanations provided herein, a multilayer ceramic capacitor with interposer is simply referred to as “capacitor with interposer,” while a multilayer ceramic capacitor is simply referred to as “capacitor,” for the sake of convenience of description. Additionally, the dimension in the lateral direction in FIG. 1 and FIG. 2 is referred to as “length,” the dimension in the vertical direction in FIG. 1 is referred to as “width,” and the dimension in the vertical direction in FIG. 2 is referred to as “height.”
The capacitor with interposer shown in FIG. 1 and FIG. 2 comprises a capacitor 100, interposer 200, and solder SOL joining the two (refer to Patent Literature 1 below, for example).
As shown in FIG. 1 and FIG. 2, the capacitor 100 is structured in such a way that it has: a dielectric chip 101 of roughly rectangular solid shape that houses multiple internal electrode layers (not illustrated) stacked in its height direction in a manner not contacting each other; and two external electrodes 102 each provided on one of the opposite end faces (end faces in the length direction) of the dielectric chip 101 in a manner partially covering the four side faces adjoining the end face and where the area partially covering the four side faces has four side faces of roughly rectangular shape; wherein the ends of some of the multiple internal electrode layers (such as odd-numbered ones from the top) are connected to one of the two external electrodes 102, while the ends of the others (such as even-numbered ones from the top) are connected to the other of the two external electrodes 102.
On the other hand, as shown in FIG. 1 and FIG. 2, the interposer 200 is structured in such a way that it has: an insulated substrate 201 of roughly rectangular sheet shape; two first conductor pads 202 of roughly rectangular shape provided on one side (top side) of the insulated substrate 201 in its thickness direction in a manner each facing one side face of roughly rectangular shape of each of the two external electrodes 102; two second conductor pads 203 of roughly rectangular shape provided on the other side (bottom side) of the insulated substrate 201 in its thickness direction in a manner facing the two first conductor pads 202, respectively; and two connection conductors 204 of roughly semi-cylindrical shape provided on the end faces of the insulated substrate 201 in its length direction, respectively; wherein one of the two first conductor pads 202 is connected to one of the two second conductor pads 203 via one of the two connection conductors 204, while the other of the two first conductor pads 202 is connected to the other of the two second conductor pads 203 via the other of the two connection conductors 204. Since the two connection conductors 204 have a roughly semi-cylindrical shape, they each have a concaved part 205 on the inner side extending in the height direction of the interposer 200.
As is evident from FIG. 2, the two first conductor pads 202 of the interposer 200 each has joined to its surface (top side), via solder SOL, one side face (bottom side) of roughly rectangular shape of each of the two external electrodes 102 of the capacitor 100.
To mount the capacitor with interposer shown in FIG. 1 and FIG. 2 on a substrate 300, cream solder is applied to the surfaces (top sides) of two conductor pads 302 provided on the surface (top side) of a substrate body 301, and the capacitor with interposer is placed in such a way that the surfaces (bottom faces) of the second conductor pads 203 contact the applied cream solder, after which the cream solder is melted by the reflow soldering method or other heat treatment and then cured, to join each second conductor pad 203 to each conductor pad 302 on the substrate 300 via solder SOL (refer to FIG. 3). It should be noted that each conductor pad 302 of the substrate 300 has a roughly rectangular profile slightly larger than that of each second conductor pad 203.
Since the capacitor with interposer shown in FIG. 1 and FIG. 2 has two connection conductors 204 of roughly semi-cylindrical shape present on the end faces of the insulated substrate 201 of the interposer 200 in its length direction, with each connection conductor 204 having the concaved part 205 on the inner side extending in the height direction of the interposer 200, as shown in FIG. 3, the melting of the cream solder and the solder SOL of the capacitor with interposer causes the molten solder to wet the end face of each external electrode 102 of the capacitor 100 via each concaved part 205 to form a fillet SOLa extending from the surface of each conductor pad 302 of the substrate 300 to the end face of each external electrode 102 of the capacitor 100.
Incidentally, if electrostriction occurs in the dielectric chip 101 due to application of voltage, especially application of alternating-current voltage, to the capacitor 100 in the mounted condition shown in FIG. 3 (repetition of a decrease in the length and increase in the height of the dielectric chip 101 (refer to the arrows) and restoration of the original length and height), this electrostriction may cause the substrate 201 to warp and then restore its original shape repeatedly to generate vibration, with the vibration generating so-called noise. Particularly when the fillets SOLa shown in FIG. 3 have been formed, tensile forces (refer to the thick arrows) based on these fillets SOLa act upon the substrate 300 to increase the warping of the substrate 300 and make it easier for the noise to generate.